1. Field of the Invention
The present invention relates to batteries and containers for batteries. More particularly, the invention relates to a battery and a container therefore having an integral molded construction and including air-flow passages through the container to facilitate heat transfer from the battery.
2. Description of the Prior Art
Energy efficient hybrid vehicles have been developed employing relatively small internal combustion engines as the vehicle prime mover and including an electric motor-generator functional during peak power demands, such as during acceleration, to provide additional acceleration power and functional during periods of deceleration or braking to convert power to electrical energy. Batteries are provided to store the electrical energy generated by the electric motor-generator during deceleration and braking and also to deliver electric power to the electric motor during acceleration.
In the operation of hybrid vehicles, the batteries are subjected to a relatively rapid discharging cycle and in normal use the batteries are subjected to only a minor or shallow discharge before being recharged. During this rapid discharging and recharging of the batteries, heat is generated by current flow through the batteries. If the battery after discharge is subsequently charged and discharged again before the heat generated has been dissipated, a heat buildup will occur and cause thermal degradation of the materials used in construction of the battery. Heat buildup also tends to cause excessive loss of electrolyte and disproportionate charging of the cells of the battery resulting in failure of the battery, The heat generation in a conventional battery used in a hybrid vehicle can be substantial because the battery is subjected to a rapid charge/discharge cycle. Furthermore, heat generation is particularly acute when the battery being charged is nearly fully charged, and the operation of hybrid vehicles normally causes only shallow discharge before recharge. Due to the generation of such heat, prior art lead-acid batteries have not been sufficiently durable for use in hybrid vehicles.
Various other applications for batteries in industrial uses or the like have required batteries which include air-flow passages through the batteries to facilitate cooling of the batteries, but none of these batteries is acceptable for use in a hybrid vehicle. Such prior art batteries are shown in U.S. Pat. No. 3,745,048, issued July 10, 1973 to Dinkler et al; U.S. Pat. No. 2,273,244, issued Feb. 17, 1942 to Ambruster; U.S. Pat. No. 2,410,952, issued Nov. 12, 1946 to Leighton; and U.S. Pat. No. 3,767,468, issued Oct. 23, 1973 to Schusler. None of these batteries shown by the prior art, however, present a functional battery which can be used in a hybrid vehicle.
The batteries of the type shown in the Dinkler et al and Schusler patents, for example, are intended to function as stationary or industrial batteries and have a rigid metal container supporting a plurality of independent cells therein. A battery having such a metal case is generally heavy and unsuitable for a vehicle intended to be energy conservative. Furthermore, these batteries do not provide a configuration which is sufficiently compact to be desireable for use in a vehicle.
Other prior art batteries, as shown in U.S. Pat. No. 3,338,452 issued Aug. 29, 1967 to Oakley et al and U.S. Pat. No. 3,147,151 issued Sept. 1, 1964 to Toce, also have a construction permitting air flow between cells of the batteries. However, such batteries would also be unsuitable for use in hybrid vehicles. The batteries shown in the Oakley et al and Toce patents include a plurality of independent cells joined together by dove-tailed connections to provide assemblies of varied numbers of cells, the number of cells being connected together being dependent on the desired size of the battery. Such batteries would not be desirable for use in a hybrid vehicle because assembly of the cells during manufacturing would be unduly expensive, the batteries would not be sufficiently compact; and the internal electrical resistance of the batteries would be too high to provide the required efficiency. This last detriment of such prior art batteries arises because relatively long connecting links are required to join the electrical terminals of the battery cells, the long connecting links resulting in increased internal electrical resistance in the battery. Furthermore, due to the rapid or frequent charge/discharge cycle of batteries in a hybrid vehicle, low internal resistance is required to decrease heat generation in the battery.